| Because of the difference between supporting of rail and treatment of subgrade in the bridge-subgrade transition section, there is the rigidity difference between bridge and subgrade. Then rail's rigidity will get abruptly change. As a result, railway will not be straight. And settlement in roadbed is not consistent with bridge abutment, which will destroy the rail smoothnessFirstly, harm and the origin of differential settlement of bridge-subgrade transition section are described and several useful treatments are compared. At the same time, recent developments on differential settlement in our country and on the world are presented. Secondly, the reinforced mechanism of bridge-subgrade transition section is analyzed emphatically. Based on theoretical analysis, a two dimensional nonlinear finite element analysis is used to analyze differential settlement of bridge-subgrade transition section whose foundation strengthened by CFG piles with different length and spacing. Results show that:(1) The subsidence basin can be mitigated when the CFG piles of railway cross section gradually change from the middle to both sides;(2) The location of the maximum settlement moves away from the abutment as the increase of density or length of piles. The scope of subgrade in bridge-subgrade transition section increases at the same time. Density or length of the CFG piles in railway vertical section gradually increased can attain the best effect. These indicate that differential settlement of bridge-subgrade section can be well controlled by using the measure of piles gradually increase density or length.(3) The strengthening scope and measures of subgrade in bridge-subgrade transition section are studied based on theoretical analysis and numerical calculation conclusions. The strengthening scope and measures to do in field transition section are discussed at the end.Some inferences are provided for the similar engineering.
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